Add in the prepared fruit to a 6- or possibly 8-qt saucepan. Stir in the sugar and butter or possibly margarine. Stirring constantly, bring the mix to a full rolling boil (a boil which doesn't stop bubbling when stirred) on high heat.

Stir in pectin quickly. Return the mix to a full rolling boil and boil exactly 1 minute, stirring constantly. Remove from heat. Skim off any foam with a metal spoon.

Ladle the jam into 1 jar at a time, leaving a 1/4-inch headspace. Wipe jar rim with a clean, damp cloth. Attach lid. Fill and close remaining jars. Process in a boiling water canner for 10 min (15 min at 1000-6000 feet: 20 min above 6000 feet).